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Capitol Illumination

The Architect of the Capitol makes the U.S. Capitol Dome, an enduring symbol of democracy recognized throughout the world, visible to all throughout the night. Learn more about the history of lighting this iconic building including the part of the Dome called the "tholos."
By Franklin Bradley | Updated March 6, 2024
        
                  Image
    The U.S. Capitol Building.

As I've walked in the dim pre-dawn light up to the Capitol during daylight saving time, I've crossed paths with scores of my Architect of the Capitol (AOC) colleagues as they head home after a full night's work. These AOC employees work each night to get the buildings of Congress and the Supreme Court ready for another day – by cleaning, repairing and maintaining them – without interfering with the work of these institutions.

While I pass my colleagues on the sidewalk walking up the hill, I watch the stars disappear from the sky as the sun's light brightens it. This week, I've also watched as the lights that illuminate the Capitol Dome at night shut off, leading me to wonder about why they're turning off at that moment, and who's making it happen.

The AOC Office of the Chief Engineer had answers to all my questions. They told me about the history of lighting in the Capitol, around the Capitol and the lighting of the Dome.

In the past, the exterior and even interior of the Dome were lit only during rare night sessions of Congress, for special occasions or holidays. Today, however, the exterior of the Dome is lit from dusk to dawn, every day of the year. These lights come on automatically, with the timing controlled by an astronomical time clock located in the basement of the Capitol. The lights that shine on the great fresco *Apotheosis of Washington* inside the Dome and illuminate the grounds around the Capitol are also controlled by that clock.

The exterior lights allow you to see a circle of columns at the very top of the Dome known as the tholos, which holds the Statue of Freedom above the Dome. Inside the tholos is what is called a convene or session light. Traditionally, it's been lit at night to signal that either the House or the Senate, or both, are in session.

When the Capitol was built, there was no reliable supply of artificial light, so the building includes skylights, cupolas and even interior light wells to provide natural light to the many rooms within. Any original lamps first burned candles or whale oil – replaced in the 1830s by kerosene, which wasn't as smelly and sooty. In the 1840s, kerosene was replaced with the newest form of fuel: natural gas.

Image
    Drawing.

One remarkable feature of the Capitol's original Bulfinch Dome in 1847 was the sight of Crutchett’s Lantern, a gas lantern which included reflectors that threw light into the Rotunda at night and could be seen miles away.This culminated in the hanging of a gas lantern that was 6 feet wide and 20 feet tall from a 100-foot-tall pine mast atop the old wooden Dome of the Capitol, which started the tradition of placing a light at the highest point of the Capitol.

Even after the introduction of electric lights, they weren't consistent enough in quality to replace gas lighting until the late 1800s. The first incandescent lights in the Capitol were installed in 1885, near the Senate Chamber, and they quickly replaced all the gas lights, so that by 1898, almost all of the Capitol was lit by electric lights.

In 1905, the Washington Times reported that on the evening before Teddy Roosevelt's inaugural ceremony, "four powerful naval searchlights poured tremendous candlepower upon the Dome," although it was still not regularly lit. For the second inauguration of Woodrow Wilson in 1917, there is a report of the Dome exterior being lit by electric floodlights, and in August of that year, it was decided that the Dome should be lit every night until midnight to "inspire the patriotic sentiment of visitors and troops passing through the city."

The practice continued through and after World War I, with advances in technology allowing smaller, more efficient floodlights to be used. There were other reasons to continue lighting the building, such as making it visible to small planes, which were became more common after Lindbergh crossed the Atlantic.

During World War II, however, the Dome was again blacked out from December 1941 through May 1945. In 1990, the lights were again updated; 60 incandescent fixtures were replaced by 38 high-intensity discharge (HID) fixtures. The new lights greatly reduced the maintenance time due to the long life of the new metal halide lamps and they reduced energy usage by 45 percent.

I'm impressed by the improvements the AOC has made throughout history to illuminate the Capitol for those who work in it and those who visit and view it from outside. As I learned, there's far more than meets the eye in the lighting of the Capitol, from the clock in the Capitol basement to the modern light fixtures hidden on the roof of the building.
THIS ARTICLE WAS ORIGINALLY PUBLISHED March 12, 2013
Comments
    
  
    
Mark Kinsler (not verified)PermalinkDecember 26, 2022 - 6:38amI just learned about the "session light" from, of all places, Cosmopolitan magazine--an issue from 1897.  Prior to Helen Gurley Brown Cosmo was a literary magazine.  The issue I've got has among other features a poem by Bret Harte, a portion of the original War of the Worlds by H G Wells, and an overwhelmingly dull exposition on higher education from Timothy Dwight, Pres. of Yale.
The advertisements, confined to the back of the magazine, feature ads for a large assortment of hospitals specializing in the cures for cancer, paralysis, alcoholism.  Also included were ads for the expensive fads of the day, namely cameras, bicycles, and music boxes.  One ad encourages the reader to sign up for a correspondence course from the American Correspondence School with the object of passing the Civil Service exam so as to land a Federal job.  It includes a line drawing of the Capitol building with the Session Light pointed out.  I'd never heard of it.  If you'd like a copy of the ad, please let me know.
ReplyRobin Comfort  (not verified)PermalinkMay 8, 2023 - 7:52amWhile visiting the Capitol at dusk, I noticed the flowers etched/embossed on the rectangular glass in the "square" lamp posts surrounding the Capitol. Is there significance to the flowers or they are just pretty?
Thank you in advance
ReplySpencer Calhoun (not verified)PermalinkDecember 22, 2023 - 3:19amHello! Great article! I was on social media and found a post about the United Kingdom Parliament having a similar light to denote that debate is occurring in the chamber. I immediately thought about this article and wondered if there was a connection of some kind?
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